The polyphenylene ethers and processes for their preparation are known in the art and described in numerous publications including Hay, U.S. Pat. No. 3,306,874 and Pat. No. 3,306,875. Other procedures are described in Van Dort, U.S. Pat. No. 3,365,422, Bennett and Cooper, U.S. Pat. No. 3,639,656, 3,642,699, 3,733,299, 3,838,102 and 3,661,848. All of these patents are incorporated herein by reference.
The processes most generally used to produce the polyphenylene ethers involve the self-condensation of a monovalent phenol in the presence of an oxygen-containing gas and a catalyst. Thereafter, chelating agents have been used to extract the catalyst into an aqueous phase which can be separated from the polymer solution or simply to form a chelate with the catalyst which is soluble in the precipitating medium (if the phases are not separated before precipitation). Antisolvents have been used to cause the polyphenylene ether polymer to precipitate.
Active catalyst systems have been developed for the preparation of polyphenylene ethers by the oxidative coupling of 2,6-di-substituted phenolic compounds. These systems are disclosed in U.S. Pat. No. 3,914,266 which is hereby incorporated by references. An example of one of the catalysts disclosed in that patent is a copper bromide complex, N,N'-di-tert-butylene-diamine, and a tertiary amine. This type of catalyst system permits fast polymerization but when employed at a high ratio of 2,6-disub-substituted phenolic compound to copper and amine, yields a polymer that appears to be of good quality, undistinguishable from that produced with other catalyst systems except that the color is usually not as good as polymer produced by, for example, copper salt-secondary amine catalyst systems. However, for reasons that are not fully understood, when polymer produced by this catalyst system is blended with styrene resins such as rubber modified polystyrene, the product has lower impact strength and poorer thermal oxidative stability, as measured by time to embrittlement at 115.degree. C than blends made from a polyphenylene ether resin prepared with the copper halide-secondary amine catalyst.
It has now been found that the inclusion of a minor amount of a secondary mono-amine in the catalyst system of U.S. Pat. No. 3,914,266 will result in the production of polyphenylene ethers having properties that permit the preparation of compositions with styrene resins which produce molded articles having good physical properties. The secondary mono-amine also aids in the phase separation of the polymer containing phase after addition of an aqueous solution containing the chelating agents as compared to a reaction mixture from a polymerization that is carried out in the absence of a secondary mono-amine.
Accordingly, it is a primary object of this invention to provide a rapid process for the preparation of polyphenylene ether resins that may be employed to produce polyphenylene ether-styrene resin compositions which have good physical properties.